The invention relates to a collector-less D-C motor with a flat stator body, flat motor coils being provided in the stator body which is inserted onto a bearing tube in which the rotor shaft is pivotably arranged (generally in two radial bearings situated at the ends of the bearing tube). Firmly attached to each of the free ends of the rotor shaft projecting out of the bearing tube is a rotor disc, at least one of which has an axially permanently magnetized magnet, and these rotor parts located at both sides of a bedplate leave an air gap into which the motor coils project.
In the case of such D-C motors designed as a disc motor with external rotor, the exciting field is commutated by an electronic commutator-type switching. This electronic commutator-type switching is triggered as a function of each rotor position by an element which is sensitive to a magnetic field, for instance a Hall element. Details of the ways and means and of the mode of action of the commutator-type switching and of the electromotive arrangement are described in the U.S.A. application of Rolf Muller, Ser. No. 363,291, assigned to Papst-Motoren KG, St. Georgen.
In connection moreover with motors of the type under consideration here, an attempt is made to obtain as narrow an air gap as possible, and then the stator bedplate must be very stiff and very accurately adjusted relative to the rotor so that it is centered within the narrow air gap and supports the motor without grazing.
One known disc-type D-C motor with external rotor has a coil supporting body of the bedplate type provided with a contoured bush into which the bearing tube is pressed. This bush requires much space, and in mass production it is also awkward to adjust it axially. The coil supporting body of the known motor is a complicated die-cast part with weak points and is not very stiff relative to deflecting forces.
The most important objects of this present invention are to improve a collector-less D-C motor of the kind indicated in the foregoing to the extent:
THAT DURING MASS PRODUCTION THE FLAT AND RELIABLY SECURED STATOR BODY CAN BE ADJUSTED EASILY AND ACCURATELY RELATIVE TO THE FIRST ROTOR DISC, AND BEING SUFFICIENTLY RIGID, AND THE WHOLE STRUCTURE WITHOUT NEED OF ADDITIONAL AXIAL LENGTH; THAT RELATIVE TO THE FIRST ROTOR DISC AND RELATIVE TO THE STATOR BEDPLATE, THE SECOND ROTOR DISC AND CONSEQUENTLY THE WIDTH OF THE AIR GAP CAN BE ADJUSTED EASILY AND ACCURATELY DURING MASS PRODUCTION; THAT THE AXIAL MAGNETIC FORCES WHICH DRAW THE ROTOR DISCS TOWARDS EACH OTHER ARE SUPPORTED IN A SIMPLE MANNER AND AS FAR AS POSSIBLE WITHOUT LOSS OF POWER; AND THAT AT POWER TAKE-OFF OF THE TORQUE THE POWER TAKE-OFF FORCES DIRECTED AT CANTING THE ROTOR SHAFT IN THE BEARINGS CAN BE AVOIDED.
These objects are achieved in the following manner: A stator bedplate known per se is secured to the bearing tube by means of a flange plate which is fastened to the bearing tube, to which the stator bedplate inserted over the bearing tube is secured while lying against it at one side. The hub of the first rotor disc has a butting face for the front end of the bearing tube facing in that direction. The hub of the first rotor disc is preferably attached so as to have a fixed seat on the rotor shaft, and the hub of the second rotor disc is slipped onto the shaft with axial play and in the direction of the first rotor disc it lies against a stop disc. The hub of the first rotor disc is preferably designed as a drive wheel with a blind hole, the floor of which is a butting face for a bearing, it being practicable that the blind hole extends above the axial center of the power take-off wheel.